Richard M. Nixon always denied it: to David Frost, to historians and to Lyndon B. Johnson, who had the strongest suspicions and the most cause for outrage at his successor’s rumored treachery. To them all, Nixon insisted that he had not sabotaged Johnson’s 1968 peace initiative to bring the war in Vietnam to an early conclusion.

Now we know Nixon lied. A newfound cache of notes left by H. R. Haldeman, his closest aide, shows that Nixon directed his campaign’s efforts to scuttle the peace talks, which he feared could give his opponent, Vice President Hubert H. Humphrey, an edge in the 1968 election. On Oct. 22, 1968, he ordered Haldeman to “monkey wrench” the initiative.